U.S. News & World Report and Best Lawyers released yesterday their inaugural ranking of law firms, but firms may not be bragging about securing the overall top spot.

Unlike U.S. News’ law school rankings, which numerically list the top 100 schools, the new project divides law firms into three tiers based on individual practice areas both nationally and in individual cities.

For instance, white-shoe New York firm Cravath, Swain & Moore has nationally six Tier 1 practices (banking and finance, corporate, general commercial litigation, mergers and acquisitions, securities/capital markets and tax), one Tier 2 (antitrust) and one Tier 3 (bankruptcy). By contrast, in the New York market it has six Tier 1 practices, three Tier 2 practices and one Tier 3 practice.

Palo Alto, Calif.-based Wilson Sonsini Goodrich & Rosati has nationally two Tier 1 (private equity and venture capital), three Tier 2 (biotechnology, mergers and acquisitions and securities/capital markets) and one Tier 3 (corporate) and highly ranked practices in San Diego, San Francisco, Seattle and Austin, Texas.

The rankings can be searched by firm name and by practice area. They include 8,782 firms ranked in 81 practice areas. The ranked firms range from large firms with multiple offices to solo practitioners in small towns.

“I don’t think that this additional ranking, in and of itself, is a game changer,” said Jeffrey Stone, co-chairman of McDermott Will & Emery, which has seven Tier 1, three Tier 2 and three Tier 3 practices nationally. “When clients are selecting attorneys, there is no single source of information that is dispositive. They look at rankings, client experience and word of mouth, among other things.”

Still, Mr. Stone said, the rankings present an incremental improvement in the information clients have available to them when hiring firms.

“Anytime you have rankings come out, it’s good to be at the top,” said Byron Myers, chief managing partner at Indianapolis-based Ice Miller. “It’s just another piece of information for clients when they choose outside counsel.”

Mr. Myers noted that the rankings might be taken seriously because of the reputations of U.S. News and Best Lawyers.

The publications determined the rankings through surveys of more than 9,000 clients and nearly as many lawyers. They took into account 3.1 million individual lawyer evaluations compiled by Best Lawyers. Lawyer experience, number of clients, billing ranges and number of transactional and litigation matters, pro bono work and diversity also counted.

“The scale of the operation was gigantic,” said Best Lawyers President Steve Naifeh. “The amount of data we collected was staggering.”

Mr. Naifeh expects the rankings to be useful for law firm clients, law students and law firms interested in checking out their competitors.

The publications ranked firms by tiers primarily because the difference between firms was too small to create a sequential list, he said.

Not everyone is convinced the rankings are a useful client resource. After U.S. News and Best Lawyers announced plans to release the new rankings, the American Bar Association’s House of Delegates voted to look into how they would be compiled. That effort continues, and New York State Bar Association President Stephen Younger remains skeptical.

“By putting firms into tiers, they have slightly alleviated the concerns that law firms would go around saying, ‘We’re the best firm in New York City or Buffalo,’” Mr. Younger said. “But the real problem with this business remains—which is that it’s totally unscientific. It’s still junk science.”

Unsophisticated clients may well put too much faith in the new rankings, he said.